///////////////////////////////////////////////////////////////
//  Copyright 2012 John Maddock. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt

#include <nil/crypto3/multiprecision/cpp_int.hpp>
#include <boost/random.hpp>
#include <boost/functional/hash.hpp>
#include <unordered_set>
#include <city.h>

//[hash1

/*`
All of the types in this library support hashing via boost::hash or std::hash.
That means we can use multiprecision types directly in hashed containers such as std::unordered_set:
*/
//]

void t1() {
    //[hash2
    using namespace nil::crypto3::multiprecision;
    using namespace boost::random;

    mt19937 mt;
    uniform_int_distribution<uint256_t> ui;

    std::unordered_set<uint256_t> set;
    // Put 1000 random values into the container:
    for (unsigned i = 0; i < 1000; ++i)
        set.insert(ui(mt));

    //]
}

//[hash3

/*`
Or we can define our own hash function, for example in this case based on
Google's CityHash:
*/

struct cityhash {
    std::size_t operator()(const nil::crypto3::multiprecision::uint256_t& val) const {
        // create a hash from all the limbs of the argument, this function is probably x64 specific,
        // and requires that we access the internals of the data type:
        std::size_t result = CityHash64(reinterpret_cast<const char*>(val.backend().limbs()),
                                        val.backend().size() * sizeof(val.backend().limbs()[0]));
        // modify the returned hash based on sign:
        return val < 0 ? ~result : result;
    }
};

//]

void t2() {
    //[hash4

    /*`As before insert some values into a container, this time using our custom hasher:*/

    std::unordered_set<uint256_t, cityhash> set2;
    for (unsigned i = 0; i < 1000; ++i)
        set2.insert(ui(mt));

    //]
}

int main() {
    t1();
    t2();
    return 0;
}

